Risk factors for anisometropia in schoolchildren: A population-based, longitudinal cohort study.

PURPOSE: To investigate the incidence rate and risk factors for anisometropia among young schoolchildren. METHODS: A population-based cohort study, the Myopia Investigation Study in Taipei, was conducted in primary schools in Taipei City. Children were recruited for biannual comprehensive eye examinations over 2 years. Cycloplegic autorefraction and slit lamp examinations were performed biannually. Data on demographic information, parental history, lifestyle and near-work activities were collected using parent-administered questionnaires at the first and final visits. Anisometropia was defined as ≥1 D difference in the spherical equivalent (SE) refractive error. RESULTS: A total of 7035 8-year-old children completed the 2-year follow-up evaluations. The average annual incidence of anisometropia was 3.8%. Multivariable logistic regression analysis revealed that baseline SE (odds ratio [OR]: 0.87 95% CI: 0.80-0.95) and female sex (OR: 1.24, 95% confidence interval [CI]: 1.02-1.50) were significantly associated with incident anisometropia. Among lifestyle risk factors, spending <1 h per day in after-school outdoor activities on weekdays (OR: 1.38, 95% CI: 1.08-1.76) and performing near work at a distance <30 cm (OR: 1.33, 95% CI: 1.08-1.64) were significantly associated with an increased risk of incident anisometropia. In the multiple linear regression analysis, the inter-eye difference in SE increased significantly in children performing near work at distances <30 cm (adjusted ß = 0.03; p = 0.02). CONCLUSIONS: This study indicated the annual incidence of anisometropia in Taiwanese schoolchildren. Less time spent outdoors and shorter eye-to-object distances during near work increased the risk of incident anisometropia.

Prevalence and Associations of Myopic Anisometropia in Chinese Adults.

PURPOSE: To investigate the prevalence and associations of myopic anisometropia in Chinese adults. METHODS: A total of 3,791 Chinese refractive surgery candidates with myopia (25.15±7.09 years old, Mean±SD) were recruited. All eyes underwent a standardized ophthalmological examination. Associations between myopic anisometropia and age, gender, spherical ametropia, astigmatism, and axial length (AL) were analyzed by means of the chi-squared test, nonparametric Kruskal-Wallis or Mann-Whitney test, binomial logistic regression analyses, and multivariate logistic regression analysis. RESULTS: The mean myopic anisometropic level was 0.96 D and prevalence of myopic anisometropia was 29.62% (defined as myopic anisometropia ≥1.00 D). The prevalence and severity of myopic anisometropia increased with age, larger interocular AL difference, and higher cylindrical power (all P<0.001). Myopic anisometropia showed a U-shaped correlation with spherical equivalent (SE) refractive error and V-shaped correlations with AL, J0 and J45. Myopic anisometropia was most strongly associated with interocular AL difference (P<0.001). CONCLUSIONS: Compared with previous reports, this study revealed an even higher prevalence of myopic anisometropia and showed a U-shaped correlation with SE and a V-shaped correlation with AL. These results indicate that the formation of myopic anisometropia could be related to neural control in the binocular AL growth balance. Further study is needed to clarify this presumption.

The burden of pure anisometropic amblyopia: a cross-sectional study on 2800 Iranians.

PURPOSE: To assess the proportion of pure anisometropic amblyopia in a sample Iranian (white) population. METHODS: A total of 2800 consecutive individuals who presented at a referral eye clinic for any reason were examined for the presence of pure anisometropic amblyopia. Anisometropia was reported when a spherical equivalent refraction difference of at least 1.0 D with or without a cylinder refraction difference of at least 1.0 D was present between the two eyes. Amblyopia was defined as the best-corrected visual acuity of 20/30 or worse or a two-line interocular visual acuity difference between eyes that could not be attributed to any structural ocular pathology or visual pathway abnormality. RESULTS: Subjects were 1528 females and 1272 males with a mean age of 30.25 ± 14.93 years (range, 5-65). Amblyopia was diagnosed in 192 cases (6.9%), significantly more frequent among females (7.9 vs. 5.7%, p = 0.02). Pure anisometropic amblyopia was present in 6.1% of the study population, significantly more common in patients with spherical hyperopic anisometropia (37.7%) compared to patients with spherical myopic anisometropia (21.3%), cylindrical myopic anisometropia (4.1%), and cylindrical hyperopic anisometropia (15%) (p < 0.001). CONCLUSIONS: Pure anisometropic amblyopia is a common finding in Caucasians seeking eye care, particularly when anisometropia is of spherical hyperopic subtype.

The prevalence of amblyogenic factors in children with persistent congenital nasolacrimal duct obstruction.

BACKGROUND: To evaluate the prevalence of amblyopia risk factors in children that underwent probing for persistent congenital nasolacrimal duct obstruction (CNLDO). METHODS: The medical records of children with CNLDO (after 1 year of age) that underwent probing were reviewed. Amblyopia risk factors, based on the American Association for Pediatric Ophthalmology and Strabismus referral criteria in 2013, were sought in the patientsʹ records before probing. The proportion of the patients with anisometropia >1.5 diopters (D) was separately calculated. In unilateral cases of CNLDO, sphere, astigmatism, and spherical equivalent of the eyes with CNLDO were compared with contralateral eyes in order to assess the effect of CNLDO on refractive error. In the follow-up examinations, the success of the probing or the need for additional procedures (Crawford intubation, Monoka intubation, or dacryocystorhinostomy) was evaluated. The prevalence of anisometropia between 'successful probing' and 'failed probing' groups was compared. RESULTS: A total of 433 cases were included in the study. 41 cases (9.46 %) had amblyopia risk factors. Twenty-four cases (5.5 %) had anisometropia >1.5 D (spherical or cylindrical). In unilateral cases of CNLDO, the sphere and spherical equivalent of the eyes with CNLDO were significantly greater than those of the contralateral eyes (p < 0.001 for both). Thirty-nine patients (9 %) required other interventions due to failure of probing (failed probing group). There were significantly more anisometropia prevalence in this group, compared with the successful probing group, at the initial examination (p = 0.03). CONCLUSIONS: The findings of greater prevalence of anisometropia >1.5 D (compared with the prevalence in the general population) and significantly greater sphere and spherical equivalents in the eye with CNLDO (compared with contralateral eye) in unilateral cases with CNLDO, suggested some relationships between anisometropia and long-term untreated CNLDO. The finding of more anisometropia in failed probing cases may support the theory of structural abnormality as an explanation for the possible relationship between congenital nasolacrimal duct obstruction and anisometropia.

Anisometropia and its association with refraction development in highly myopic children.

CLINICAL RELEVANCE: Anisometropia can affect visual development in children. Investigations of anisometropia in high myopes would explore potential causes related to anisometropia, highlighting the management of anisometropia in high myopia. BACKGROUND: The prevalence of anisometropia ranged from 0.6% to 4.3% in general paediatric population and from 7% to 14% in myopes. Anisometropia is regarded as an associated factor for myopia development, while myopia progression is a stimulus driving anisometropic development. The purpose of this study was to investigate the prevalence of anisometropia and its association with refraction development in Chinese children with high myopia. METHODS: In the cohort study, a total of 1,577 highly myopic (spherical equivalent ≤-5.0D) children aged 4-18 years were included. Refractive parameters (dioptre of sphere, dioptre of cylinder, corneal curvature radius, and axial length) of both eyes were measured after cycloplegia. The prevalence and degree of anisometropia were compared among refractive groups (non-parametric tests or chi-square tests), and regression analyses were used to determine associated factors of anisometropia. The statistical significance was set to P < 0.05 (two-tailed). RESULTS: In highly myopic children with a mean (standard deviation) age of 13.06 (2.80) years, the proportions of spherical equivalent anisometropia, cylindrical anisometropia and spherical anisometropia ≥1.00 D were 34.5%, 21.9% and 39.9%, respectively. There was more spherical equivalent anisometropia associated with more severe astigmatism (P for trend <0.001). In the multivariate regression analysis, more spherical equivalent anisometropia, cylindrical anisometropia and spherical anisometropia were associated with higher degrees of astigmatism (standard beta = -0.175, -0.148 and -0.191, respectively). More spherical anisometropia was associated with better spherical power (standard beta = 0.116). CONCLUSION: The proportion of anisometropia in highly myopic children was high, compared with previously reported general population, and more severe anisometropia was associated with higher degree of cylindrical power, but not spherical power.

Prevalence, Associated Factors, and Inter-Eye Differences of Refractive Errors in a Population-Based Japanese Cohort: The Tohoku Medical Megabank Eye Study.

PURPOSE: To investigate the prevalence, associated factors, and inter-eye differences of myopia and astigmatism in an adult Japanese population-based cohort. METHODS: A total of 4282 participants from the Tohoku Medical Megabank Organization Eye Study (ToMMo Eye Study) underwent comprehensive ocular examinations as well as extensive physiological tests and a lifestyle questionnaire. The spherical equivalent (SE) and cylinder power were obtained as refractive parameters. The age- and gender-stratified prevalences of high myopia (SE < -5D), myopia (SE < -0.5D), hyperopia (SE > 0.5D), astigmatism (cylinder power < -0.5D), and anisometropia (SE difference >1D) were calculated. Multivariable analyses were performed to identify associated factors for refractive error (RE). Distribution and associated factors of the inter-eye difference in RE were also investigated. RESULTS: The age-adjusted prevalence of high myopia, myopia, hyperopia, astigmatism, and anisometropia was 15.9%, 63.5%, 14.7%, 51.1%, and 14.7%, respectively. Both myopia and high myopia were more prevalent in the younger age group, while astigmatism was more prevalent in the older age group. Age, education, blood pressure, intraocular pressure, and corneal thickness are significantly associated with myopic refraction. Age, gender, intraocular pressure, and corneal thickness are correlated with astigmatism. Older age was associated with against-the-rule astigmatism. Older age, myopia, and longer education showed a significant correlation with large inter-eye differences in SERE. CONCLUSIONS: This study demonstrated the high prevalence of myopia in young Japanese, which may be caused by a generational shift. This study also confirmed the influence of age and education on both the prevalence and inter-eye differences of RE.

Prevalence of anisometropia and its associated factors in school-age children.

PURPOSE: To determine the prevalence of anisometropia and the associated demographic and biometric risk factors in children. METHODS: This cross-sectional study was conducted on the elementary school children of Shahroud, east of Iran, in 2015. All rural students were recruited, while multistage cluster sampling was used to select the students in urban areas. All children underwent optometric examinations including the measurement of uncorrected and corrected visual acuity, autorefraction, and subjective refraction with cycloplegia. Biometric components were measured using the Allegro Biograph. Myopia and hyperopia were defined as a spherical equivalent ≤-0.5 and ≥ +2.00 diopter, respectively. Students with a history of ocular trauma or lack of cycloplegic refraction at least in one eye were excluded from the study. RESULTS: Of 6624 selected children, 5620 participated in the study. After applying the exclusion criteria, the data of 5357 students (boys: 52.8%, n = 2834) were analyzed. The mean age of the subjects was 9.2 ± 1.7 years (range: 6-12 years). The prevalence of anisometropia ≥ 1 D was 1.1% (95% CI: 0.8 to 1.4) in all children, 1.0% (95% CI: 0.7-1.3) in boys, 1.3% (95% CI: 0.8-1.7) in girls, 1.1% (95% CI: 0.8-1.4) in urban children, and 1.4% (95% CI: 0.5-2.3) in rural children. The prevalence of anisometropia was 8.8% (95% CI: 5.3-12.2) in myopic and 5.7% (95% CI: 2.8-8.5) in hyperopic children. Axial length asymmetry (OR = 40.9; 95%CI: 10.2-164.1), myopia (OR = 17.9; 95% CI: 9.4-33.9), and hyperopia (OR = 10.1; 95% CI: (5.1-19.7) were associated with anisometropia in multiple logistic regression model. More anisometropia was associated with more severe amblyopia. The odds of amblyopia (OR = 82.3: 38.2-177-3) and strabismus (OR = 17.6: 5.5-56.4) were significantly higher in anisometropic children. The prevalence of amblyopia was 21.7% in children with myopic anisometropia ≥ 3D, 66.7% in children with hyperopic anisometropia ≥ 3D, and 100% in cases with antimetropia ≥ 3D. CONCLUSION: The prevalence of anisometropia was low in Iranian school children. However, a high percentage of anisometropic students had amblyopia and strabismus. Axial length was the most important biometric component associated with anisometropia.

Correlation of Refractive Error with Anisometropia Development in Early Childhood.

PURPOSE: This study aims to investigate the relationship between the type and severity of refractive error and anisometropia development in preschool children. DESIGN: Retrospective cohort study. METHODS: Data from Maccabi Healthcare Services, Israel's second-largest Health Maintenance Organization (HMO), were analyzed. The study included all isometropic children aged 1 to 6 years, re-examined for refraction at least 2 years following their initial examination between 2012 and 2022. Anisometropia was defined as a ≥1 diopter interocular difference in spherical equivalent. Relationships were assessed using logistic regression models adjusted for key sociodemographic factors. RESULTS: Among 33,496 isometropic children (51.2% male, mean age 3.2 ± 1.5 years), the prevalences of emmetropia, myopia, and hyperopia were 26.7% (n = 8944), 4.2% (n = 1397), and 69.1% (n = 23,155), respectively. Over a mean follow-up period of 5.1 ± 2.4 years, 2593 children (7.7%) were diagnosed with anisometropia. Adjusted odds ratios (ORs) for anisometropia gradually increased with baseline refractive error severity, reaching 13.90 (5.32-36.34) in severe myopia and 4.19 (3.42-5.15) in severe hyperopia. This pattern was also evident in cylindrical anisometropia, where ORs increased with greater baseline astigmatism, peaking at 12.10 (9.19-15.92) in children with high astigmatism (≥3 D). Associations remained consistent in sensitivity and subgroup analyses including across both sexes and when using a stricter anisometropia criterion. CONCLUSIONS: Children aged 1 to 6 years, initially without anisometropia but showing increasing severity of myopia, hyperopia, or astigmatism, are more likely to develop anisometropia. This underscores the importance of follow-up refractive measurements within this population to promptly diagnose and treat anisometropia and prevent potential visual complications.

Refractive features and amblyopia in Duane's Retraction Syndrome: A review of the 582 patients.

PURPOSE: To report the visual and refractive characteristics and the prevalence of amblyopia in patients with different types of Duane's Retraction Syndrome (DRS). METHOD: This retrospective study was performed on hospital records of 582 DRS patients at Farabi Hospital, Iran, from 2012 to March 2022. RESULTS: The mean age of patients was 19.4 ± 11.9 (range, 3-70) years [335 (57.6 %) females and 247 (42.4 %) males (P < .001)]. DRS type I, II, III, and IV were presented in 347 (59.6 %), 148 (25.4 %), 82 (14.1 %), and 5 (0.9 %) patients, respectively. There were 530 (91.1 %) patients with unilateral and 52 (8.9 %) with bilateral involvement. In the unilateral patients, the DRS eyes' corrected distance visual acuity (CDVA) and astigmatism were significantly worse than the Non-DRS Eyes (P < .001). The mean amount of all refractive and visual parameters in bilateral patients' right or left eyes was significantly lower than in unilateral patients' non-DRS eyes (all P < .05). Anisometropia was observed in 75(12.9 %) of the patients. Amblyopia was observed in 18.5 % (98 patients) and 36.5 % (19 patients) of unilateral and bilateral DRS patients, respectively (P < .001). In unilateral patients, amblyopia was found in 57 (16.4 %) patients with Type I, 22 (14.9 %) patients with Type II, 16 (19.5 %) patients with Type III, and 3 (60 %) patients with Type IV. Forty-four (37.6 %) of patients with amblyopia had anisometropia. CONCLUSION: This large-scale study indicates that DRS types differ in terms of refractive error, visual acuity, and the prevalence of amblyopia and anisometropia. Clinicians should be aware of the clinical features associated with different types of DRS.

Prevalence of anisometropia and influencing factors among school-age children in Nantong, China: a cross-sectional study.

Objective: To investigate the prevalence of anisometropia and associated parameters among school-aged children in Nantong, China. Methods: This school-based, cross-sectional study examined students from primary schools, junior high schools, and senior high schools in an urban area of Nantong, China. Univariate and multivariate logistic regression analyses were used to investigate the specific correlations between anisometropia and related parameters. Non-cycloplegic autorefraction was assessed for each student. Anisometropia was defined as the spherical equivalent refraction (SE) difference ≥ 1.0 D between eyes. Results: A total of 9,501 participants were validated for analyses, of which 53.2% (n = 5,054) were male, and 46.8% (n = 4,447) were female. The mean of age was 13.32 ± 3.49 years, ranging from 7-19 years. The overall prevalence of anisometropia was 25.6%. Factors such as myopia, scoliosis screening positive, hyperopia, female sex, older age, and higher weight had a significantly higher risk of anisometropia (p < 0.05). Conclusion: There was a high prevalence of anisometropia in school-age children. Some physical examination parameters are closely related to children's anisometropia, especially myopia and scoliosis. Preventing myopia and controlling its progression may be the most important ways to reduce the prevalence of anisometropia. Correcting scoliosis may be an important factor in controlling the prevalence of anisometropia, and maintaining good reading and writing posture may be helpful in controlling the prevalence of anisometropia.

[Investigations on the prevalence of axial and refractive anisometropia]. / Badania nad czestoscia wystepowania anizometropii osiowej i refrakcyjnej.

PURPOSE: The aim of this paper was to describe the prevalence of axial and refractive anisometropia among students 18 years old. MATERIAL AND METHODS: The study was carried out among high school students 18 years old in Szczecin, Poland. A total of 1040 students including 381 boys and 659 girls were examined. Every student underwent retinoscopy after cycloplegia using 1% Tropicamide. The differences in spherical equivalents in the right and left eye, were calculated. Students who had anisometropia >1.00 Dsph, were qualified to the next part of the studies, in which examinations using an autorefractometer, keratometer, biometric ultrasounds as well as the IOL Master were carried out. In the group of 70 students (which makes up 7% of the examined population), qualified to the next part of the examinations, a total of 20 participants (2%) declined. The remaining 50 students (5%) were divided into two groups. One group consisted of students with axial anisometropia, while the other consisted of students with refractive anisometropia. All of the collected data were stored in an electronic database using the Microsoft EXCEL computer program and analyzed with Statistica 6.1 software. In the analysis of nominal variables the Fisher exact test was used. P values of less than 0.05 were considered statistically significant. RESULTS: In the conducted studies a higher prevalence of axial anisometropia (60%) compared to refractive anisometropia (40%) was observed, but the difference did not reach statistical significance (p = 0.20). No association between the type of anisometropia and gender was found in the studies. Axial anisometropia was found in 60% of boys and girls in the study group qualified to the second part of the examinations, while refractive anisometropia was found in 40% of boys and girls qualified to the next part of the examinations. CONCLUSIONS: Anisometropia in students 18 years old is caused more often by different axial length rather than by different refraction of the eye.

Anisometropia Profile in Elderly Population: Tehran Geriatric Eye Study.

PURPOSE: To investigate the distribution and prevalence of anisometropia according to age, gender and ocular biometry in a geriatric population in Tehran, Iran. METHODS: The present study was conducted on the geriatric population aged above 60 years. The study participants were selected using stratified random cluster sampling. The uncorrected and best-corrected visual acuity, dry objective (ARK510A, Nidek Co. 42 LTD, Aichi, Japan) and subjective refraction and ocular biometry (IOL Master 500; Carl Zeiss Meditec, Jena, Germany) were recorded for each patient. The magnitude and prevalence of anisometropia were evaluated in association with influential factors in cut-points of 0.50, 1.00, 1.50 and 2.00 diopter (D). RESULTS: The mean age of participants (3237 individuals, 54% were female) was 68.19 ± 6.48 (range: 60-97) years. The mean anisometropia in the whole sample was 0.82 D (95% CI: 0.76 - 0.88 D), which increased from 0.62 D (in those aged 60-64 years old) to 1.36 D (in those above 80 years). The prevalence of anisometropia >1 D in total population, males, and females were 23.81%, 24.9%, and 22.76%, respectively. The odds ratio of anisometropia was higher in cases with cataracts, myopia compared to emmetropia, keratometry asymmetry, axial length asymmetry (P = .001), and corneal diameter asymmetry (all others, P < .001). CONCLUSION: The results of the present study show a high prevalence of anisometropia in elderly population, which was related to refractive error, cataract, age, gender, and ocular biometry asymmetry.

The prevalence of refractive error in schoolchildren.

CLINICAL RELEVANCE: Information on the refractive error prevalence in school-aged children will result in delivering the optimal eye health service to this group. BACKGROUND: Understanding the prevalence of refractive error in school-aged children is crucial to reduce the consequences of uncorrected refractive error. This study aims to investigate the prevalence of refractive error among school-aged children in Shiraz, Iran. METHODS: In this cross-sectional population-based study, 2001 schoolchildren aged 6-12 years participated. All participants underwent cycloplegic refraction. Spherical equivalent (SE) of -0.50 dioptre or more was considered as myopia, SE of +2.00 dioptre or more as hyperopia, and astigmatism as cylinder power of 0.75 dioptre or more. The difference of 1.00 dioptre or more between two eyes defined as anisometropia. RESULTS: The prevalence of myopia was 11.6% (95% confidence interval [CI]: 10.2-13.1%), hyperopia 6.7% (95%CI: 5.6-7.9%), and astigmatism 28.9% (95%CI: 26.9-31.0%), out of which 82.1% had with the rule astigmatism. Anisometropia was detected in 4.0% (95%CI: 3.2-5.0%) of children. Astigmatism and anisometropia were significantly higher in boys (p < 0.001, p = 0.03 respectively). The SE decreased significantly with increasing age (p < 0.001) indicating an increase in myopia with age. In addition, the rate of myopic astigmatism increased with age (p < 0.001). Among studied schoolchildren 97.0% could achieve the best-corrected visual acuity of 6/6 and 3.0% could not in the better eye. CONCLUSION: Astigmatism was the most common refractive error among primary school children. The prevalence of myopia was relatively higher than other studies conducted in Iran, and it increased with age. These results may highlight the role of lifestyle changes and increased near work activities on the myopic shift in school-aged children. The findings provide information for screening programmes in school-aged children.

Prevalence of anisometropia and associated factors in Shandong school-aged children.

Objective: To investigate anisometropia's prevalence and associated factors in school-aged children. Methods: A cross-sectional school-based study was conducted in Shandong Province, China, including children aged 4 to 17 from 9 schools. Anisometropia was defined as the differences between the two eyes in spherical equivalent (SE) or cylinder degree of 1.00 diopter (D) or more [SE or cylindrical (CYL) difference ≥ 1.00 D] after cycloplegic autorefraction. The Generalized Linear Model (GLM) was used to analyze the effects of ocular parameters [the differences between eyes in axial length (AL), habitual visual acuity (HVA), and corneal astigmatism (CA)] and lifestyle parameters (time spent indoor near work and outdoor activities) on anisometropia. Results: Total 4,198 (93.4%) of the 4,494 children were included in the statistical analysis. The mean difference in inter-eye SE was 0.42 ± 0.61 D. The prevalence of anisometropia was 13.2% (95%CI: 12.1 to 14.2%) (SE anisometropia's prevalence:10.3%; CYL anisometropia's prevalence: 4.1%), increased with older age (OR = 1.10, P = 0.002), the worse myopic eye (myopia vs. premyopia, OR = 1.87, P = 0.002), the worse hyperopic eye (hyperopia vs. premyopia, OR = 1.77, P = 0.013), larger difference in inter-eye AL (0.1-0.3 vs. ≤ 0.1, OR = 1.67, P = 0.008; >0.3 vs. ≤ 0.1, OR = 28.61, P < 0.001), HVA (>0.2 vs. ≤ 0.2, OR = 3.01, P < 0.001), CA (OR = 6.24, P < 0.001), the worse stereoacuity (>100 vs. ≤ 100, OR = 1.59, P = 0.001), longer indoor near work time per day on weekends (4-8 vs. <4, OR = 1.41, P = 0.038; ≥8 vs. <4, OR = 1.40, P = 0.131), and shorter outdoor activity time per day on weekdays (≥1 vs. <1, OR = 0.75, P = 0.046) in multivariable analysis. In the SE anisometropia group, the difference in inter-eye AL (>0.3 vs. ≤ 0.1, ß: 0.556, 95%CI: 0.050 to 1.063), HVA (>0.2 vs. ≤ 0.2, ß: 0.511, 95%CI: 0.312 to 0.710), and CA (ß: 0.488, 95%CI: 0.289 to 0.688), stereoacuity (>100 vs. ≤ 100, ß: 0.299, 95%CI: 0.110 to 0.488) had a positive impact on the difference in inter-eye SE. Conclusions: Ocular parameters and lifestyle parameters are associated with the occurrence of anisometropia in children aged 4 to 17 years, including the difference in inter-eye AL, HVA, CA, stereoacuity, indoor near work time, and outdoor activity time. Preventing myopia and early treating anisometropic amblyopia may be effective ways to reduce the prevalence of anisometropia.

Amblyopia among Patients Attending the Outpatient Department of Ophthalmology of a Tertiary Care Centre: A Descriptive Cross-sectional Study.

Introduction: Amblyopia is defined as a reduction in visual acuity unilaterally or bilaterally without any detectable cause. It is a major public health issue in developing and underdeveloped countries. Its prevalence is usually underestimated because of proper study and lack of awareness. The aim of the study was to find out the prevalence of amblyopia among patients attending the Outpatient Department of Ophthalmology of a tertiary care centre. Methods: This descriptive cross-sectional study was conducted among outpatients visiting a tertiary care centre in the Outpatient Department of Ophthalmology between 1 January 2017 to 31 December 2019. Ethical approval was obtained from the Institutional Review Board (Registration number: 407/2020 P). All patients had gone through a comprehensive eye examination. Convenience sampling was used. Point estimate and 99% Confidence Interval were calculated. Results: Among 82972 patients, prevalence of amblyopia was 344 (0.41%) (0.37-0.46, 99% Confidence Interval). Amblyopia was more common in anisometropia 263 (63.50%). A total of 117 (34%) patients had no history of eye examination and were newly diagnosed with amblyopia. Astigmatism was the most common type of refractive error among 224 (56.70%) amblyopic patients. Conclusions: The prevalence of amblyopia was found to be lower than in previous studies conducted in similar settings. Early detection and diagnosis of amblyopia can help to design more effective plans and treatments to reduce amblyopia through optical correction and amblyopia therapy. Keywords: amblyopia; anisometropia; astigmatism; refractive errors.

Anisometropia and refractive status in children with congenital nasolacrimal duct obstruction-a prospective observational study.

PURPOSE: To assess the refractive status and anisometropia in children with unilateral and bilateral congenital nasolacrimal duct obstruction (CNLDO). METHODS: Consecutive children newly diagnosed with CNLDO were prospectively enrolled from November 2017 to May 2019. A complete ophthalmic evaluation including cycloplegic refraction was performed followed by appropriate intervention. Patients were followed for 6 months, and cycloplegic refraction was performed at each visit. The final refractive error was defined as the refractive error obtained from the most recent visit. Amblyogenic risk factors were assessed based on 2013 referral criteria of the American Association for Pediatric Ophthalmology and Strabismus (AAPOS). RESULTS: A total of 308 patients with CNLDO were enrolled: 205 (67%) unilateral cases and 103 (33%) bilateral cases. In unilateral cases, the affected eye and unaffected fellow eye showed statistically significant difference in terms of sphere (P < 0.001), cylinder (P = 0.019), and spherical equivalent (P < 0.001); there was no interocular difference in bilateral cases (P > 0.05). Anisometropia was more prevalent in unilateral cases than in bilateral cases (11.2% vs 1.9%; P = 0.005). Based on the 2013 AAPOS referral criteria, 3.9% of the unilateral and 3.9% of bilateral cases exhibited amblyogenic risk factors. Later age of presentation was associated with higher rate of anisometropia (53.8% in the age group >48 months). CONCLUSIONS: In our study cohort, unilateral CNLDO was associated with a higher prevalence of anisometropia compared with bilateral CNLDO. The affected eye in unilateral CNLDO had higher prevalence of refractive error.

Prevalence of anisometropia in children and adolescents.

Background: This research was developed to study the epidemiology of anisometropia. It aims to estimate the prevalence of anisometropia in Portuguese children and adolescents at various educational stages, studying its association with sociodemographic variables. Methods: Observational cross sectional study envolving 749 children and adolescents (from 3 to 16 years old) from the central region of Portugal. The refraction was performed with a paediatric, open field auto refractometer (PlusOptix), without cycloplegia and under binocular conditions, to determine the rate of anisometropia and its association with gender, study cycle and area of residence. Results: The prevalence of anisometropia in the studied sample was 6.1%, varying from 2.9% in pre-school education to 9.4% in the 3rd study cycle. Myopic anisometropia was the most prevalent and hyperopic and astigmatic anisometropia showed identical proportions of occurrence. No statistical differences were found between genders or between areas of residence regarding the rate of anisometropia. Regarding spherical equivalent anisometropia, there was a pattern of variation that increased with the cycle of studies (p = 0.012), with myopic anisometropia being the main contributor to this variation. Conclusions: This study found an increase in anisometropia with the educational stage. The high rate of anisometropia found in adolescents (9.4%) as well as the progressive increase in this rate throughout school progress (from 2.9% to 9.4%) suggests the need to extend the detection strategies of this condition beyond childhood.

What can anisometropia tell us about eye growth?

BACKGROUND/AIMS: Both eyes of one individual share the same environment and genes. We examined interocular differences in biometry to determine the potential role of other factors in refractive development. METHODS: 362 subjects (6-7 years) from the Northern Ireland Childhood Errors of Refraction study were studied. Cycloplegic autorefraction was measured with a Shin-Nippon open-field autorefractor. Axial length and corneal curvature were measured with a Zeiss IOLMaster. RESULTS: 257 subjects had an interocular difference of <0.50 D (ISO group) and 105 (29%) a difference of ≥0.50 D (ANISO group). Twenty-five subjects (6.9%) had anisometropia ≥1.00 D and 9 (2.5%) had anisometropia ≥1.50 D. The two groups, ISO and ANISO, showed different refractive distributions (p=0.001) with the ISO group showing a nearly Gaussian distribution and the ANISO group showing positive skew, a hyperopic shift and a bi-Gaussian distribution. A marker of emmetropisation is the poor correlation between refraction and corneal curvature seen in older children. There was no significant correlation between refraction and corneal curvature of each eye in the ISO group (r=0.09, p=0.19), but these parameters were significantly correlated in the ANISO group (r=0.28, p=0.004). CONCLUSION: In young children, small degrees of anisometropia (≥0.5 D) are associated with impaired emmetropisation. This suggests that anisometropia is a marker for poorly regulated eye growth, indicating that, in addition to environmental and genetic influences on eye growth, stochastic processes contribute to refractive outcomes.

Prevalence of strabismus and its risk factors among school aged children: The Hong Kong Children Eye Study.

The study aims to determine the prevalence of strabismus and its risk factors among school children in Hong Kong. This is a cross-sectional study involving 6-8 year old children from different districts in Hong Kong. 4273 children received comprehensive ophthalmological examination, cycloplegic auto-refraction, best corrected visual acuity (BCVA), anterior segment examination, cover/uncover test, ocular motility, and fundus examination. Demographic information, pre- and post- natal background, parental smoking status, and family history of strabismus were obtained through questionnaires. Strabismus was found among 133 children (3.11%, 95% CI 2.59-3.63%), including 117 (2.74%) exotropia and 12 (0.28%) esotropia cases (exotropia-esotropia ratio: 9.75:1). There was no significant difference in prevalence across age (6-8 years) and gender. Multivariate analysis revealed associations of strabismus with myopia (≤ - 1.00D; OR 1.61; 95% CI 1.03-2.52; P = 0.037) hyperopia (≥ + 2.00D; OR 2.49; 95% CI 1.42-4.39; P = 0.002), astigmatism (≥ + 2.00D; OR 2.32; 95% CI 1.36-3.94; P = 0.002), and anisometropia (≥ 2.00D; OR 3.21; 95% CI 1.36-7.55; P = 0.008). Other risk factors for strabismus included maternal smoking during pregnancy (OR 4.21; 95% CI 1.80-9.81; P = 0.001), family history of strabismus (OR 6.36; 95% CI 2.78-14.50, P < 0.0001) and advanced maternal age at childbirth (> 35 years; OR 1.65; CI 1.09-2.49, P = 0.018). The prevalence of strabismus among children aged 6-8 years in Hong Kong is 3.11%. Refractive errors, family history of strabismus and maternal smoking history during pregnancy are risk factors. Early correction of refractive errors and avoidance of maternal smoking during pregnancy are potentially helpful in preventing strabismus.

Refraction in Preschool Children in Kazanlak, Bulgaria.

INTRODUCTION: The refractive state of the eye changes as the eye's axial length increases and the cornea and lens flatten. In general, eyes are hyperopic at birth, become slightly more hyperopic until the age of 7, which at this point we see a myopic shift toward plano until the eyes reach their adult dimensions, usually by about the age 16. AIM: To determine the prevalence of refractive error in preschool children aged 3 - 6 in the city of Kazanlak, Bulgaria. MATERIALS AND METHODS: A cross-sectional study was conducted in a kindergarten based school within the city of Kazanlak, Bul-garia. Out of 15 kindergarten schools, 10 chose to participate in the study. The children underwent non-mydriatic refraction screening using a Plus-Optix S12с mobile camera. Myopia, hyperopia and astigmatism were defined as being a spherical equivalent (SE) ≤ -0.50 D, SE ≥ +2.00 D and cylindrical diopters ≤ -1.00 D. RESULTS: A total of 596 children were screened. Out of these 596 children; 526 were with ametropia (470 hypermetropia, 46 myopia) and 50 had astigmatism. Strabismus was found in 12 children, with a further 8 children suffering from amblyopia and finally 8 children were also found to be diagnosed with anisometropia. In 8 cases there were no results due to opacities or due to the small size of the pupil. CONCLUSION: The prevalence of refractive error in preschool children is similar to that found in other research in the field. While most cases fall into the category of emmetropia or mild hypermetropia, most of the children had never been to an ophthalmologist. A manda-tory checkup should be issued for all children below the age of seven.